Single/Dingle setup with 1 round ring and one oval?- Mtbr.com
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  1. #1
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    Single/Dingle setup with 1 round ring and one oval?

    I've been thinking about running a dinglespeed setup on a fat bike. One reasonable gear that I could still commute a good distance on, and one nice low gear for trailer pulling in snow. My frame doesn't have adjustable chainstay length, so without playing the sizing game, would there be a way I could run say 32/18 for the reasonable gear and like a 24oval/26T low. I don't know exactly if these are even close to running the same chain length, I was just throwing out numbers, but would an oval narrow wide on the low gearing help keep the chain on & make up for the lack of tension in the low setting assuming the high setting has decent tension?

  2. #2
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    Don't know about oval chainrings. But I have had a round nw with 10 speed derailleur and I have never dropped the chain. I don't think oval shape will do anything more to keep the chain on.

    I would suggest to make sure the chain remains in sufficient tension on both dingle gearings.

    I once had a dingle speed mtb with chaintensioner and it was terrible. I don't recommend a tensioner.
    Instagram: kimthecyclist

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  3. #3
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    In theory, you could use the same chain length for both ratios since the 24/26 is -/+ 8 from the 32/18. The issue as touched on above is the chain tension with the length of chain also based on the chainstay length. Both of these ratios would have to be magic gears without the use of a tensioner for your chainstay. Also, the tensioner would have to be moved inbound/outbound to preserve chainline. Perhaps it would be possible to set it in between, but then again the chain may certainly pop off easily too. There is no eccentric fat bike hub that I know of, the Singular puffin has an EBB but not sure of other fatbikes. Why not 1x with a med cage RD?
    I don't know why,... it's just MUSS easier to pedal than the other ones.

  4. #4
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    I think the odds of finding magic dingle gears are pretty low. Even if you get the high gear at perfect tension, the low gear will be noticeably slacker with an 8t spread. I run a 2t spread dingle on my bike with an EBB and it can be tricky to set the tension just right for both gears. Running narrow-wides may improve slack-chain retention in low gear, but will also limit magic gear options since you canít use a half-link. A slack chain can work ok if your chain line is spot-on, but in my experience it isnít reliable enough for hard riding. Pulling a trailer in a really low gear may cause frame flex that could encourage chain drop.

    You can definitely do a dingle with a tensioner, but you should get a tensioner that allows side-to-side movement of the pulley such as the DMR STS. This will mean you donít have to adjust the chain line of the tensioner when shifting.

    Have you considered a 2x1 setup with a Paul Melvin? This would be two chainrings and a single cog. You could shift it with a front derailleur or manually by hand. You would have many more choices for ratios. You could also use a rear derailleur as a tensioner, since a clutch would be a benefit and you could use larger cogs (Melvin canít clear larger than 20t cogs).

  5. #5
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    Prepare yourself for math!

    I run a 36/18 high and a 32/22 low without a chain tensioner and no narrow wide chainring without any issues. Thats +/-4 tooth spread. I do however get a little chain slap noise on super rough trails. My high gear tension is a bit tight and the low is a bit loose.

    Maintaining an equal total number of teach for each speed is a good rule of thumb. And in practice I've done a +/-2 tooth spread and my current +/-4 tooth is fine too. I've heard of people doing a +/-6 without a chain tensioner but I haven't tried it myself.

    To help figure this out before I bought chainrings and cogs I made a little excel spreadsheet to calculate the actual chain length for different speeds. I did this because maintaining the total number of teach for each gear isn't perfect. The chain length changes because of the different distance between contact points of the chainring and cog. I did a little writeup on this in my blog. Check it out if you want to find out more. You can also download the excel spreadsheet tool if you want: Singlespeed & Dinglespeed Gearing
    Singlespeed & Dinglespeed Gearing

    If I understand your question right you want to run a +/-8 tooth setup.
    24chainring / 26cog
    32chainring / 18cog

    When I plug that into my calculator I get a chain length difference of 1.96mm. Which isn't too bad because my current setup calculates to 1.69mm difference. I think it will work without a chain tensioner. But if you can, go for narrow-wide chainrings.
    Only other suggestion I have is spend the time to get your chainline perfect.

  6. #6
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    Non adjustable chain stay length is going to be a challenge. As mentioned above a magic gear on some CS lengths in certain gearing can be hard to achieve, add a second gearing ratio and the problem multiplies. IME with oval SS's and dingles I don't think the oval would help make up the difference in chain tension/slack but you'll only know if you set it up and try. I've only done round dingles, never round/oval or double oval.

    Some good info and dingle stoke in here....
    http://forums.mtbr.com/singlespeed/m...ds-991379.html
    @adamalphabet

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